1. Field of the Invention
This invention relates to an adjustable control system for the weft on a weaving loom. more specifically, this is a control mechanism which enables the weft thread to be controlled according to a predetermined fixed pattern and the control mechanism to be adjusted while the machine is in operation, according to measured results of weft movement.
2. Background of Invention and Prior Art
More specifically, this invention also relates to a control in weaving machines in which the weft is inserted in the shed by means of a master jet mechanism powered by compressed air and supported for movement through the shed by auxiliary jet mechanisms located in the shed.
In such a weaving machine there will be as many master jet mechanisms and weft storage units, more specifically a thread bobbin and a so-called storage drum, as there are numbers of different types of weft threads which will make up the fabric concerned. It is also known that it is necessary for the control of different types of weft thread to vary weft speed in order to reduce to a minimum the risk of weaving faults with the best possible chance of successful weft thread movement. Indeed, it is known that a slower timing sequence must be followed for a heavier and/or smoother weft thread. In other words, a lower weft movement speed must be selected than would be used for lighter or rougher yarns. It is further known that one of the control parameters of the above-mentioned air jet weaving machines is the timing sequence according to which the thread movement is controlled, i.e. the time in each weaving cycle at which the control of each component begins (control time) on one hand and the duration of this control, the duration time, on the other hand.
The first object of the invention is thus related to the fact that the timing sequence of the components which are used for the movement of the weft thread is adapted to the type of weft thread inserted for each shot. For this purpose, a number of timing sequences are introduced into the control mechanism of the weaving machine which correspond to the weft threads to be woven. Thus, a specific timing sequence stored in the control mechanism is used for the control of the components involved in the movement of the weft thread, depending on the weft thread to be inserted at a particular moment.
It is obvious that when a specific type of thread is inserted, the duration time of the control of a component of the control mechanism can thus vary from zero to a maximum value, wherein the duration time will be set at zero not only for the control of the storage drums and the master jet mechanisms for the wefts which are not involved at that point in the weaving cycle in progress, but also for a certain number of auxiliary jets should this be required due to the thread movement.
The second object of the invention consists of the installation of mechanisms in the path of the weft thread movement which enable certain measurements to be made relating to the weft thread movement. These measurements consist primarily of determining the time taken between the departure of the weft thread at the insertion end of the shed and the arrival of the head of the weft thread in particular at the other end of the shed. In this process the signal from the weft stop motion, which as already known observes the head of the weft thread at the end of the weft movement, may be used for this latter measurement.
As specified according to the invention, for each type of weft thread and taking the type of weft thread concerned into account, the time thus measured is used to modify and optimize the timing sequence associated with a specific type of weft thread and subsequently, subject to observance of the physical order in the timing sequence for the control of the consecutive jet mechanisms, to progressively change the parameters of this order until an adequate speed of the weft movement is obtained.
Thus the control obtained is not only adapted to the maximum obtainable speed for the movement of a specific type of weft thread but, in addition, a highly efficient consumption of compressed air is also achieved.
A mechanism as specified according to the invention which demonstrates the aforementioned and other characteristics is of the type which contains a separate master jet for each type of weft, to which the appropriate operating pressure is applied according to the type of weft thread, in which this master jet is supplied from a separate storage drum and whereby the auxiliary jets also operate with a regulated operating pressure and both the master jets and the auxiliary jets are controlled according to a specific timing sequence. This type of mechanism is also characterized by the fact that at least the control time and/or the duration time of the master jets are adjusted according to a measurement made during the weaving operation.